Most modern automotive fuel systems utilize fuel injectors to provide precise metering of fuel for introduction into each combustion chamber of an internal combustion engine. The fuel injectors atomize the fuel during injection, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected, and allowing an oxidizer, typically ambient air, to thoroughly mix with the fuel prior to combustion. The metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine. Thus, as a general rule, the greater the precision in metering and targeting of the fuel, and the greater the atomization of the fuel, the lower the emissions and the greater the fuel efficiency.
The fuel injector is typically mounted upstream of the intake valve in the intake manifold proximate a cylinder head. As the intake valve opens on an intake port of the cylinder, fuel is sprayed towards the intake port. In one situation, it may be desirable to target the fuel spray at the intake valve head or stem while in another situation, it may be desirable to target the fuel spray at the intake port instead of at the intake valve. In both situations, the targeting of the fuel spray can be affected by the spray pattern. Where the spray pattern has a large divergent cone shape, the sprayed fuel may impact on a surface of the intake port rather than towards its intended target. Conversely, where the spray pattern has a narrow divergent cone shape, the fuel may not atomize and may even recombine into a liquid stream. In either case, incomplete combustion may result, leading to an increase in undesirable exhaust emissions.
Complicating the requirements for targeting and spray pattern are cylinder head configuration and intake geometry specific to different engine designs. As a result, a fuel injector designed for a specified cone pattern and targeting of the fuel spray may work extremely well in one type of engine configuration but may present emissions problems upon installation in a different type of engine configuration.
An electromagnetic fuel injector typically utilizes a solenoid assembly to supply an actuating force to a fuel metering assembly. Typically, the fuel metering assembly is a plunger-style closure member which reciprocates between a closed position, where the closure member is positioned in a seat to prevent fuel from escaping through a metering orifice into the combustion chamber, and an open position, where the closure member is lifted from the seat, allowing fuel to discharge through the metering orifice for introduction into the combustion chamber. In reciprocating between the open and closed position, the closure member is positioned by a lower guide member that facilitates a proper contact with the seat. In known fuel injectors the lower guide member and the seat are two separate parts that need to be properly aligned during assembly of the fuel injector. A misalignment of the two parts may cause leakage of the fuel injector that will adversely affect precision metering and targeting of the fuel. To prevent such misalignment, the lower guide member and the seat have been formed as one homogeneous member. However, in known homogeneous lower guide and seat members, atomization and precision targeting of fuel can not be altered so as to meet particular requirements for different engine configurations.
It would be beneficial to develop a fuel injector having a lower guide member and a seat member in precise alignment, and in which atomization and precision targeting of fuel can be altered so as to meet particular requirements for different engine configurations.